<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - Cleanup</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    #root {
      position: absolute;
      left: 0;
      top: 0;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
  </body>
<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js"
  }
}
</script>

<script type="module">
import * as THREE from 'three';

class ResourceTracker {

	constructor() {

		this.resources = new Set();

	}
	track( resource ) {

		if ( resource.dispose || resource instanceof THREE.Object3D ) {

			this.resources.add( resource );

		}

		return resource;

	}
	untrack( resource ) {

		this.resources.delete( resource );

	}
	dispose() {

		for ( const resource of this.resources ) {

			if ( resource instanceof THREE.Object3D ) {

				if ( resource.parent ) {

					resource.parent.remove( resource );

				}

			}

			if ( resource.dispose ) {

				resource.dispose();

			}

		}

		this.resources.clear();

	}

}

function main() {

	const canvas = document.querySelector( '#c' );
	const renderer = new THREE.WebGLRenderer( { antialias: true, canvas } );

	const fov = 75;
	const aspect = 2; // the canvas default
	const near = 0.1;
	const far = 5;
	const camera = new THREE.PerspectiveCamera( fov, aspect, near, far );
	camera.position.z = 2;

	const scene = new THREE.Scene();
	const cubes = []; // an array we can use to rotate the cubes

	function addStuffToScene() {

		const resTracker = new ResourceTracker();
		const track = resTracker.track.bind( resTracker );

		const boxWidth = 1;
		const boxHeight = 1;
		const boxDepth = 1;
		const geometry = track( new THREE.BoxGeometry( boxWidth, boxHeight, boxDepth ) );

		const loader = new THREE.TextureLoader();
		const texture = loader.load( 'resources/images/wall.jpg' );
		texture.colorSpace = THREE.SRGBColorSpace;

		const material = track( new THREE.MeshBasicMaterial( {
			map: track( texture ),
		} ) );
		const cube = track( new THREE.Mesh( geometry, material ) );
		scene.add( cube );
		cubes.push( cube ); // add to our list of cubes to rotate
		return resTracker;

	}

	function waitSeconds( seconds = 0 ) {

		return new Promise( resolve => setTimeout( resolve, seconds * 1000 ) );

	}

	async function process() {

		for ( ;; ) {

			const resTracker = addStuffToScene();
			await waitSeconds( 2 );
			cubes.length = 0; // remove the cubes
			resTracker.dispose();
			await waitSeconds( 1 );

		}

	}

	process();

	function resizeRendererToDisplaySize( renderer ) {

		const canvas = renderer.domElement;
		const width = canvas.clientWidth;
		const height = canvas.clientHeight;
		const needResize = canvas.width !== width || canvas.height !== height;
		if ( needResize ) {

			renderer.setSize( width, height, false );

		}

		return needResize;

	}

	function render( time ) {

		time *= 0.001;

		if ( resizeRendererToDisplaySize( renderer ) ) {

			const canvas = renderer.domElement;
			camera.aspect = canvas.clientWidth / canvas.clientHeight;
			camera.updateProjectionMatrix();

		}

		cubes.forEach( ( cube, ndx ) => {

			const speed = .2 + ndx * .1;
			const rot = time * speed;
			cube.rotation.x = rot;
			cube.rotation.y = rot;

		} );

		renderer.render( scene, camera );

		requestAnimationFrame( render );

	}

	requestAnimationFrame( render );

}

main();
</script>
</html>
